Metal nitride material for thermistor, method for producing same, and film type thermistor sensor

ABSTRACT

The metal nitride material for a thermistor consists of a metal nitride represented by the general formula: (M 1 - v A v ) x Al y (N 1-w O w ) z  (where “M” represents at least one of Ti, V, Cr, Mn, Fe, and Co, “A” represents at least one of Sc, Zr, Mo, Nb, and W, 0.0&lt;v&lt;1.0, 0.70≦y/(x+y)≦0.98, 0.45≦z≦0.55, 0&lt;w≦0.35, and x+y+z=1), wherein the crystal structure thereof is a hexagonal wurtzite-type single phase.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a U.S. Utility Application under 35 U.S.C. 111 whichclaims the priority benefit of Japanese Application No. 2013-167525,filed Aug. 12, 2013; Japanese Application No. 2013-167527, filed Aug.12, 2013; Japanese Application No. 2013-180297, filed Aug. 30, 2013;Japanese Application No. 2013-180309, filed Aug. 30, 2013; and JapaneseApplication No. 2013-182743, filed Sep. 4, 2013, the entire contents ofthe aforementioned applications are hereby incorporated herein byreference.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a metal nitride material for athermistor, which can be directly deposited on a film or the likewithout firing, a method for producing the same, and a film typethermistor sensor.

Description, of the Related Art

There is a demand for a thermistor material used for a temperaturesensor or the like having a high B constant in order to obtain a nighprecision and high sensitivity thermistor sensor. Conventionally,transition metal oxides such as Mn, Co, Fe, and the like are typicallyused as such thermistor materials (see Patent Documents 1 to 3). Thesethermistor materials need a heat treatment such as firing or the like ata temperature of 550° C. or higher in order to obtain a stablethermistor characteristic/property.

In addition to thermistor materials consisting of metal oxides asdescribed above. Patent Document 4 discloses a thermistor materialconsisting of a nitride represented by the general formula:M_(x)A_(y)N_(z) (where “M” represents at least one of Ta, Nb, Cr, Ti,and Zr, “A” represents at least one of Al, Si, and B, 0.1≦x≦0.8, O≦y≦0.6, 0.1≦z≦0.08, and z+y+z=1). In Patent Document 4, only aTa—Al—N-based material consisting of a nitride represented by thegeneral formula: M_(x)A_(y)N_(z) (where 0.5<x≦0.8, 0.1≦y≦0.5, 0.2≦z≦0.7,and x+y+z=1) is described in an Example. The Ta—Al—N-based material isproduced by sputtering in a nitrogen gas-containing atmosphere using amaterial containing the element (s) listed above as a target. Theresultant thin film is subject to a heat treatment at a temperature from350 to 600° C. as required.

Other than thermistor materials, Patent, document 5 discloses aresistance film macenal for a strain sensor, which consists of a nitriderepresented by the general formula; Cr_(100-x-y)N_(x)M_(y) (where “M” isone or more elements selected from Ti, V, bb, Ta, Ni, Zr, Hf, Si, Ge, C,O, P, Se, Te, Zn, Cu, Bi, Fe, Mo, W, As, Sn, Sb, Pb, B, Ga, In, Tl, Ru,Rh, Re, Os, Ir, Pt, Pd, Ag, Au, Co, Be, Mg, Ca, Sr, Ba, Mn, Al, and rareearth elements, the crystal structure thereof is composed of mainly abcc structure or mainly a mixed structure of a bcc structure and A15type structure, 0.0001≦X≦30, 0≦y≦30, and 0.0001≦x+y≦50). The resistancefilm material for a strain, sensor is employed for measuring strain andstress from changes in the resistance of the sensor made of a Cr—N-basedstrained resistance film, where both of the amounts of nitrogen (x) andan accessory component element(s) b (y) are 30 at % or lower, as well asfor performing carious conversions. The Cr—N—M-based material isproduced by reactive sputtering in a deposition atmosphere containingthe accessory gaseous element(s) using a material containing theabove-described element (s) or the like as a target. The resultant thinfilm is subject to a heat treatment at a temperature from 200 to 1000°C. as required.

PRIOR ART DOCUMENTS Patent Documents

[Patent Document 1] Japanese Patent Laid-open No. 2000-068110

[Patent Document 2] Japanese Patent Laid-Open No. 2000-348903

[Patent Document 3] Japanese Patent Laid-Open No. 2006-324520

[Patent Document 4] Japanese Patent Laid-open No. 2004-319737

[Patent Document 5] Japanese Patent laid-Open No. H10-270201

SUMMARY OF THE INVENTION

[Problems to be Solved by the Invention]

The following problems still remain in the conventional techniquesdescribed above.

In recent years, the development of a film type thermistor sensor madeof a thermistor material formed on a resin film has been considered; andthus, it has been desired to develop a thermistor material that can bedirectly deposited on a film. Specifically, it is expected that aflexible thermistor sensor will be obtained by using a film.Furthermore, it is desired to develop a very thin, thermistor sensorhaving a thickness of about 0.1 mm. However, a substrate material usinga ceramic such as alumina that has often been conventionally used has aproblem that if the substrate material is thinned to a thickness of 0.1mm for example, the substrate material is very fragile and breakseasily. Thus, it is expected that a very thin thermistor sensor will beobtained by using a film.

However, a film made of a resin material typically has a low heatresistance temperature of 150° C. or lower, and even polyimide, which isknown as a material having a relatively high heat resistancetemperature, only has a heat resistance temperature of about 200° C.Hence, when a neat treatment is performed in a process of forming athermistor material, it has been conventionally difficult to use such athermistor material. The above-described conventional oxide thethermistor material needs to be fired at a temperature of 550° C. orhigher in order to realize a desired thermistor characteristic, so thata film type thermistor sensor that is directly deposited on a filmcannot be realized. Thus, it has been desired to develop a thermistormaterial that can be directly deposited on a film without firing.However, even the thermistor material disclosed in Patent Document 4still needs a heat treatment on the resultant thin film at a temperaturefrom 350 to 600° C. as required in order to obtain a desired thermistorcharacteristic. Regarding this thermistor material, a B constant ofabout 500 to 3000 K was obtained in an Example of the Ta—Al—N-basedmaterial, but the heat resistance of this material is nor described andtherefore, the thermal reliability of a nitride-based material isunknown.

In addition, the Cr—N—M-based material disclosed in Parent document 5has a low B constant, of 500 or lower and cannot ensure heat resistanceto a temperature of 200° C. or lower unless a heat treatment in therange of 200° C. to 1000° C. is performed, and thus, a film typethermistor sensor that, is directly deposited on a film cannot berealized. Therefore, it has been desired to develop a thermistormaterial that can be directly deposited on a film without firing.

The present invention has been made in view of the aforementionedcircumstances, and an object of the present invention is to provide ametal nitride material for a thermistor, which has high reliability andhigh heat resistance and can be directly deposited on a film or the likewithout firing, a method for producing the same, and a film typethermistor sensor.

[Means for Solving the Problems]

The present inventors' serious endeavor carried out by focusing on anAl—N-based material among nitride materials found that the Al—N-basedmaterial having a good B constant, and excellent heat resistance may beobtained without firing by substituting the Al site with a specificmetal, element for improving electric conductivity and by ordering itinto a specific crystal structure even though Al—N is an insulator anddifficult to provide with an optimum thermistor characteristic (Bconstant: about 1000 to 6000 K).

Therefore, the present invention has been made on the basis of the abovefinding, and adopts the following configuration in order to overcome theaforementioned problems.

Specifically, a metal nitride material for a thermistor according to afirst aspect of the present invention is characterized by a metalnitride material for a thermistor, which consists of a metal nitriderepresented by the general formula:(M_(1-v)A_(v))_(x)Al_(y)(N_(1-w)O_(w))_(z) (where “M” represents atleast one of Ti, V, Cr, Mn, Fe, and Co, “A” represents at least one ofSc, Zr, Mo, Nb, and W, 0.0<v<1.0, 0.70≦y/(x+y)≦0.98, 0.45≦z≦0.55,0<w≦0.35, and x+y+=1), wherein the crystal structure thereof is ahexagonal wurtzite-type single phase.

Since the metal nitride material for a thermistor consists of a metalnitride represented by the general formula:(M_(1-v)A_(v))_(x)Al_(y)(N_(1-w)O_(w))_(z) (where “M” represents atleast one of Ti, V, Cr, Mn, Fe, and Co, “A” represents at least one ofSc, Zr, Mo, Nb, and W, 0.0<v<1.0, 0.70≦y/(x+y)≦0.98, 0.45≦z≦0.55,0<w≦0.35, and x+y+=1), wherein the crystal structure thereof is ahexagonal wurtzite-type single phase, a good B constant and excellentheat resistance can be obtained without firing. In particular, the heatresistance can be further improved by the effect of oxygen (O) includedin a crystal so as to compensate nitrogen defects in the crystal or tointroduce interstitial oxygen therein, or the like.

Note that, when the value of “y/(x+y)” (i.e., Al/(M+A+Al)) is less than0.70, a wurtzite-type single phase cannot he obtained, but twocoexisting phases of a wurtzite-type phase and a NaCl-type phase or asingle phase of only a NaCl-type phase may be obtained, so that asufficiently high resistance and a high B constant cannot be obtained.

When the value of “y/(x+y)” (i.e., Al/(M+A+Al)) exceeds 0.98, the metalnitride material exhibits very high resistivity and extremely highelectrical insolation, so that the metal nitride material is notapplicable as a thermistor material.

When the value of “z” (i.e., (N+O)/(M+A+Al+N+O)) is less than 0.45, theamount of nitridation is too small to obtain a wurtzite-type singlephase. Consequently, a sufficiently high resistance and a high Bconstant cannot be obtained.

In addition, when the value of “z” (i.e., (N+O)/(M+A+Al+N+O)) exceeds0.50, a wurtzite-type single phase cannot be obtained. This is becausethe stoichiometric ratio of (N+O)/(M+A+Al+N) in a wurtzite-type singlephase in the absence of defects at the nitrogen site is 0.5 (.i.e.,N(M+A+Al+N=0.5, and because the stoichiometric ratio of(N+O)/(M+A+Al+N+O) when all defects at the nitrogen site are compensatedby oxygen is 0.5 (i.e., (N+O)/(M+A+Al+N+O)=0.5). The amount of “z”exceeding 0.5 may be due to the interstitial oxygen introduced in acrystal or due to the quantitative accuracy of the light elements(nitrogen, oxygen) in an XPS analysis.

In addition, in this study, when the value of “w” (i.e., O/(N+O))exceeded 0.35, a wurtzite-type single phase could not be obtained. Thereason will be understandable considering the fact that when w=1,y/(x+y)=0, and v=1, a corundum-type Sc₂O₃ phase is formed in the case of“A”=Sc, a fluorite-type ZrO_(z) phase is formed in the case of “A”=Zr, arutile-type MoO₂ phase or a MoO₃ phase having the same crystal structureas rhenium trioxide (ReO₃) is formed in the case of “A”=Mo, arutile-type NbO₂ phase is formed in the case of “A”=Nb, and a distortedrutile-type WO₂ phase is formed in the case of “A”=W; when w=1, y/(x+y)=0, and v=0, a rutile-type (M1)O₂ phase, a corundum-type (M2)₂O₃ phase,a spinel-type (M3)₃O₄ phase (where “M1” represents Ti, “M2” representsV, Cr , or Fe, and “M3” represents Mn or Co) is formed; and when w=1 andy/(x+y) =1, a corundum-type Al₂O₃ phase is formed. It has been foundthat when the value of “w” increases and the amount of oxygen increaseswith respect to the amount of nitrogen, it is difficult to obtain awurtzite-type single phase. Therefore, it has been found in this studythat a wurtzite-type single phase can be obtained only when O/(N+O) is0.35 or less.

A metal nitride material for a thermistor according to a second aspectof the present invention is characterized in that the metal nitridematerial for a thermistor according to the first aspect of the presentinvention is deposited as a film, and is a columnar crystal extending ina vertical direction with respect to the surface of the film.

Specifically, since she metal nitride material for a thermistor is acolumnar crystal extending in a vertical direction with respect to thesurface of the film, the crystallinity of the film is high, so that highheat resistance can be obtained.

A metal nitride material for a thermistor according to a third aspect ofthe present invention is characterised in that the metal nitridematerial according to the first or the second aspect of the presentinvention is deposited as a film, and is more strongly oriented along ac-axis than an a-axis in a vertical direction with respect to thesurface of the film.

Specifically, since the metal nitride material for a thermistor is morestrongly oriented along the c-axis than the a-axis m a verticaldirection with respect to the surface of the film, a high B constant ascompared with the case of the strong a-axis orientation, and anexcellent reliability in heat resistance can be obtained.

A film type thermistor sensor according to a fourth aspect of thepresent invention is characterised by including an insulating film; athin film, thermistor portion made of the metal nitride material for athermistor according to any one of the first to third aspects of thepresent invention on the insulating film; and a pair of patternelectrodes formed at least on the top or the bottom of the thin filmthermistor portion.

Specifically, since, in the film type thermistor sensor, the thin filmthermistor portion made of the metal nitride material for a thermistoraccording to any one of the first to third aspects of the presentinvention is formed on the insulating film, an insulating film havinglow heat resistance such as a resin film can be used because the thinfilm thermistor portion is formed without firing and has a high Bconstant arid high heat resistance, so that a thin and flexiblethermistor sensor having an excellent thermistor characteristic can beobtained.

A substrate material employing a ceramic such as alumina that has often,been conventionally used has a problem that if the substrate material isthinned to a thickness of 0.1 mm for example, the substrate material isvery fragile and breaks easily. On the other hand, since a film can beused in the present invention, a very thin film type thermistor sensorhaving a thickness of 0.1 mm can be obtained.

A method for producing a metal nitride material for a thermistoraccording to a fifth aspect of the present invention is characterised,in that the method for producing the metal nitride material for athermistor according to any one of the first to third aspects of thepresent invention includes a deposition step of performing filmdeposition by sputtering (reactive spattering) in a nitrogen- andoxygen-containing atmosphere using an M-A-Al alloy sputtering target(where represents at least one of Ti, v, Cr, Ma, Fe, and Co, and “A”represents at least one of Sc, Zr, Mo, Nb, and W).

Specifically, since, in the method for producing the metal nitridematerial for a thermistor, the film deposition is performed by reactivesputtering in a nitrogen- and oxygen-containing atmosphere using anM-A-Al alloy sputtering target, the metal nitride material for athermistor or the present invention, which consists of a metal nitriderepresented by the aforementioned general formula: (M,A)_(x)Al_(y)(N,O)_(z) ( “M” represents at least one of Tif V, Cr, Mn,Fe, and Co, and “A” represents at least one of Sc, Zr, Mo, Nb, and W)can be deposited on a film without firing.

[Effects Of The Invention]

According to the present invention, the following effects may beprovided.

Specifically, since the metal nitride material for a thermistoraccording to the present invention, consists of a metal nitriderepresented by the general formula:(M_(1-v)A_(v))_(x)Al_(y)(N_(1-w)O_(w))_(z) (where “M” represents atleast one of Ti, V, Cr, Mn, Fe, and Co, “A” represents at least one ofSc, Zr, Mo, Nb, and W, 0.0<v<1.0, 0.70≦y/(x+y)≦0.98, 0.45≦z≦0.55,0<w≦0.35, and x+y+z=1), wherein the crystal structure thereof is ahexagonal wurtzite-type single phase, the metal nitride material havinga good B constant and excellent heat resistance can be obtained withoutfiring. Also, since, in the method for producing the metal nitridematerial, for a thermistor according to the present invention, filmdeposition is performed by reactive sputtering in a nitrogen- andoxygen-containing atmosphere using an M-A-Al alloy sputtering target(where “M” represents at least one of Ti, V, Cr, Mn, Fe and Co, and “A”represents at least one of Sc, Zr, Mo, Nb, and W), the metal nitridematerial for a thermistor of the present invention, which consists of ametal nitride represented by the aforementioned general formula; (M,A)_(z)Al_(y)(N,O)_(z), can be deposited on a film without firing.Furthermore, since, in the film, type thermistor sensor according to thepresent invention, a thin film thermistor portion made of the metalnitride material for a thermistor according to the present invention isformed on an insulating film, a thin and flexible thermistor sensorhaving an excellent thermistor characteristic can be obtained by usingan insulating film such as a resin film having low heat resistance.Furthermore, since a substrate material is a resin film rather than aceramic that becomes very fragile and breaks easily when being thinned,a very thin film type thermistor sensor having a thickness of 0.1 mm canbe obtained.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a (Ti+Sc)—Al—(N+O)-based ternary phase diagram illustratingthe composition range of a metal nitride material for a thermistoraccording to one embodiment of a metal nitride material for athermistor, a method for producing the same, and a film type thermistorsensor of the present invention.

FIG. 2 is a (Ti+Zr)—Al—N+O)-based ternary phase diagram illustrating thecomposition range of a metal nitride material for a thermistor accordingto one embodiment of a metal nitride material for a thermistor, a methodfor producing the same, and a film type thermistor sensor of the presentinvention.

FIG. 3 is a (Ti+Mo)—Al—(N+O)-based ternary phase diagram illustratingthe composition range of a metal nitride material for a thermistoraccording to one embodiment of a metal nitride material for athermistor, a method for producing the same, and a film type thermistorsensor of the present invention.

FIG. 4 is a (Ti+Nb)—Al—(N+O)-based ternary phase diagram illustratingthe composition range of a metal nitride material for a thermistoraccording to one embodiment of a metal nitride material for athermistor, a method for producing the same, and a film type thermistorsensor of the present invention.

FIG. 5 is a (Ti+W)—Al—(N+O)-based ternary phase diagram illustrating thecomposition range of a metal nitride material for a thermistor accordingto one embodiment of a metal nitride material for a thermistor, a methodfor producing the same, and a film type thermistor sensor of the presentinvention.

FIG. 6 is a perspective view illustrating a film type thermistor sensoraccording to the present embodiment.

FIG. 7 is a perspective view illustrating a method for producing a filmtype thermistor sensor in the order of the steps according to thepresent embodiment.

FIG. 8 is a front view and a plan view illustrating a film evaluationelement for a metal nitride material for a thermistor according to anExample of a metal nitride material for a thermistor, a method forproducing the same, and a film type thermistor sensor of the presentinvention.

FIG. 9 is a graph illustrating the relationship between a resistivity at25° C. and a B constant according to Examples and a Comparative Exampleof the present invention in the case where “M”=Ti, “A”=Sc.

FIG. 10 is a graph illustrating the relationship between a resistivityat 25° C. and a B constant according to Examples and a ComparativeExample of the present invention in the case where “M”=Ti, “A”=Zr.

FIG. 11 is a graph illustrating the relationship between a resistivityat 25° C. and a B constant according to Examples and ComparativeExamples of the present invention in the case where “M”=Ti, “A”=Mo.

FIG. 12 is a graph illustrating the relationship between, a resistivityat 25° C. and a B constant according to Examples and a ComparativeExample of the present invention in the case where “M”=Ti, “A”=Nb.

FIG. 13 is a graph illustrating the relationship between a resistivityat 25° C. and a B constant according to Examples and a ComparativeExample of the present invention in the case where “M”=Ti, “A”=W.

FIG. 14 is a graph illustrating the relationship between theAl/(Ti+Sc+Al) ratio and the B constant, according to Examples and aComparative Example of the present invention.

FIG. 15 is a graph illustrating the relationship between theAl/(Ti+Zr+Al) ratio arid the B constant according to Examples and aComparative Example of the present invention.

FIG. 16 is a graph illustrating the relationship between theAl/(Ti+Mo+Al) ratio and the B constant, according to Examples andComparative examples of the present invention.

FIG. 17 is a graph illustrating the relationship between theAl/(Ti+Nb+Al) ratio and the B constant according to Examples and aComparative Example of the present invention.

FIG. 18 is a graph illustrating the relationship between theAl/(ti+W+Al) ratio and the B constant according to Examples and aComparative Example of the present invention.

FIG. 19 is a graph illustrating the result of X-ray diffraction (XRD) inthe case of a strong c-axis orientation, where Al/(Ti+Sc+Al)=0.81according to an Example of the present invention.

FIG. 20 is a graph illustrating the result of X-ray diffraction (XRD) inthe case of a strong c-axis orientation, where Al/(Ti+Zr+Al)=0.84according to an Example of the present invention.

FIG. 21 is a graph illustrating the result of X-ray diffraction (XRD) inthe case where a strong c-axis orientation, where Al/(Ti+Mo+Al)=0.93according to an Example of the present invention.

FIG. 22 is a graph illustrating the result of X-ray diffraction (XRD) inthe case where a strong c-axis orientation, where Al/(Ti+Nb+Al)=0.83according to an Example of the present invention.

FIG. 23 is a graph illustrating the result of X-ray diffraction (XRD) inthe case where a strong c-axis orientation, where Al/(Ti+W+Al)=0.76according to an Example of the present invention.

FIG. 24 is a cross-sectional SEM photograph illustrating the materialexhibiting a strong c-axis orientation according to Example of thepresent invention in the case where “M”=Ti, “A”=Sc.

FIG. 25 is a cross-sectional SEM photograph illustrating the materialexhibiting a strong c-axis orientation according to Example of thepresent invention in the case where “M”=Ti, “A”=Zr.

FIG. 26 is a cross-sectional SEM photograph illustrating rhe materialexhibiting a strong c-axis orientation according to Example of thepresent invention in the case where “M”=Ti, “A”=Mo.

FIG. 27 is a cross-sectional SEM photograph illustrating the materialexhibiting a strong c-axis orientation according to Example of thepresent invention in the case where “M”=Ti, “A”=Nb.

FIG. 28 is a cross-sectional SEM photograph illustrating the materialexhibiting a strong c-axis orientation according to Example of thepresent invention in the case where “M”=Ti, “A”=W.

DESCRIPTION OF THE EMBODIMENTS

Hereinafter, a description will be given of a metal nitride material fora thermistor, a method for producing the same, and a film typethermistor sensor according to one embodiment of the present inventionwith reference to FIGS. 1 to 7. In the drawings used in the followingdescription, the scale of each component is changed as appropriate sothat each component is recognizable or is readily recognized.

The metal nitride material for a thermistor of the present embodimentconsists of a metal nitride represented by the general formula:(M_(1-v)A_(v))_(x)Al_(y)(N_(1-w)O_(z) (where “M” represents at least oneof Ti, V, Cr, Mn, Fe, and Co, “A” represents at least one of Sc, Zr, Mo,Nb, and W, 0.0<v<1.0, 0.70≦y/(x+y)≦0.98, 0.45≦z≦0.55, 0<w≦0.35, andx+y+z=1), wherein the crystal structure thereof is a hexagonalwurtzite-type (space group: P6₃mc (No. 186)) single phase.

For example, in the case where “M”=Ti, “A”=Sc, the metal nitridematerial for a thermistor of the present embodiment consists of a metalnitride represented by the general formula:(Ti_(1-v)Sc_(v))_(x)Al_(y)(N_(1-w)O_(w))_(z) (where 0.0<v <1.0,0.70≦y/(x+y)≦0.98, 0.45≦z≦0.55, 0<w≦0.35, and x+y+z=1), wherein thecrystal structure thereof is a hexagonal wurtzite-type single phase.Specifically, the metal nitride material for a thermistor consists of ametal nitride having a composition within the region enclosed by thepoints A, B, C, and D in the (Ti+Sc (scandium))-Al-(N+O)-based ternaryphase as shown in FIG. 1, wherein the crystal phase thereof iswurtzite-type.

In the case where “M”=Ti, “A”=Zr, the metal nitride material for athermistor of the present, embodiment consists of a metal nitriderepresented try the general formula:(Ti_(1-v)Zr_(v)Zr_(v))_(x)Al_(y)(N_(1-w)O_(w))_(z) (where 0.0<v<1.0,0.70≦y/(x+y)≦0.98, 0.45≦z≦0.55, 0<w≦0.35, and x+y+z=1), wherein thecrystal structure thereof is a hexagonal wurtzite-type single phase.Specifically, the metal nitride material for a thermistor consists of ametal nitride having a composition within the region enclosed by thepoints A, B, C, and D in the (Ti+Zr (zirconium)-Al—(N+O)-based ternaryphase diagram as shown in FIG. 2, wherein the crystal phase thereof iswurtzite-type.

In the case where “M”=Ti, “A”=Mo, the metal nitride material for athermistor of the present embodiment consists of a metal nitriderepresented by the general formula:(Ti_(1-v)Mo_(v))_(x)Al_(y)(N_(1-w)O_(w))_(z) (where 0.0<v<1.0,0.70≦y/(x+y)≦0.98, 0.45≦z≦0.55, 0<w≦0.35, and x+y+z=1), wherein thecrystal structure thereof is a hexagonal wurtzite-type single phase.Specifically, the metal nitride material for a thermistor consists of ametal nitride having a composition within the region enclosed by thepoints A, B, C, and D in the (Ti+Mo (molybdenum))-Al—(N+O)-based ternaryphase diagram as shown in FIG. 3, wherein the crystal phase thereof iswurtzite-type.

In the case where “M”=Ti, “A”=Nb, the metal nitride material for athermistor of the present embodiment consists of a metal nitriderepresented by the general formula:(Ti_(1-v)Nb_(v))_(x)Al_(y)(N_(1-w)O_(w))_(z) (where 0.0<v<1.0,0.70≦y/(x+y)≦0.98, 0.45≦z≦0.55, 0<w≦0.35, and x+y+z=1), wherein thecrystal structure thereof is a hexagonal wurtzite-type single phase.Specifically, the metal nitride material for a thermistor consists of ametal nitride having a composition within the region enclosed by thepoints A, B, C, and D in the Ti+Nb (niobium))-Al—(N+O)-based ternaryphase diagram as shown in FIG. 4, wherein the crystal phase thereof iswurtzite-type.

In the case where “M”=Ti, “A”=W, the metal nitride material for athermistor of the present embodiment consists of a metal nitriderepresented by the general formula:(Ti_(1-v)W_(v))_(x)Al_(y)(N_(1-w)O_(w))_(z) (where 0.0<v<1.0,0.70≦y/(x+y)≦0.98, 0.45≦z≦0.55, 0<w≦0.35, and x+y+z=1), wherein thecrystal structure thereof is a hexagonal wurtzite-type single phase.Specifically, the metal nitride material for a thermistor consists of ametal nitride having a composition within the region enclosed by thepoints A, B, C, and D in the (Ti+W (tungsten))-Al—(N+O)-based ternaryphase diagram as shown in FIG. 5, wherein the crystal phase thereofwurzite-type.

Note that the composition ratios or (x, y, z) (at %) at the points A, B,C, and D are A (x, y, z=13.5, 31.5, 55.0), 8 (x, y, z=0.9, 44.1, 55.0),C (x, y, z=1.1, 53.9, 45.0), and D (x, y, z=16.3, 38.5, 45.0),respectively.

As described above, the wurtzite-type crystal structure belongs to thehexagonal space group of P6₃mc (No. 186), and Ti, A, and Al (where “A”represents at least one of Sc, Zr, Mo, Nb and W) are present at the sameatomic site, that is, they are in a so-called solid solution forexample, in the case of “Ti_(0.08)Mo_(0.02)Al_(0.9)N”, Ti, Mo, and Alare present at the same atomic site with the probability of 8%, 2%, and90%, respectively). The wurtzite-type crystal structure is a structurein which the vertexes of (Ti, A, Al) N₄ tetrahedron are connected eachother and the nearest-neighbor site of the (Ti, A, Al) site is N(nitrogen), whereby (Ti, A, Al) is four-coordinated by nitrogen.

Note that, other than Ti, V (vanadium), Cr (chromium), Mn (manganese) ,Fe (iron) , and Co (cobalt can also be present at the same atomic siteas Ti in the above crystal structure, and can be an element of M. Theeffective ionic radius is a physical property that is often used inorder to determine the interatomic distance. In particular, using wellknown literature values for the ionic radius by Shannon, it is logicallyassumed that a wurtzite-type (V, A)Al—N—O, (Cr, A)Al—N—O, (Mn, A)Al—N—O,(Fe, A) Al—N—O, and (Co, A)Al—N—O (where “A” represents at least: one ofSc, Zr, Mo, Nb, and W) structure can be obtained. Here, the oxygen (O)is oxygen that compensates nitrogen defects in a crystal or isinterstitial oxygen.

Table 1 shows the effective ionic radius of each ion species of Al, Ti,V, Cr, Mn, Fe, and Co (ref., R, D. Shannon, Acta Crysta.) logr. , Sect,A, 32, 751 (1976)).

TABLE 1 UNIT: nm FOUR-COORDINATED SIX-COORDINATED STRCUTURE STRCUTURE(REFERENCE) ION IONIC ION IONIC SPECIES RADIUS SPECIES RADIUS Al³⁺ 0.039Al³⁺ 0.0535 Ti⁴⁺ 0.042 Ti³⁺ 0.067 V⁵⁺ 0.0355 V³⁺ 0.064 Cr⁴⁺ 0.041 Cr³⁺0.0615 Cr⁵⁺ 0.0345 Mn²⁺ 0.066 Mn³⁺ (HS) 0.0645 Mn⁴⁺ 0.039 Mn⁵⁺ 0.033Mn³⁺ (LS) 0.058 Fe²⁺ 0.063 Fe³⁺ (HS) 0.0645 Fe³⁺ 0.049 Fe³⁺ (LS) 0.055Co²⁺ 0.058 Co³⁺ (HS) 0.061 Co⁴⁺ 0.04 Co³⁺ (LS) 0.0545

The wurtzite-type crystal structure exhibits a four-coordinatedstructure. Referring to the effective ionic radius relative to Mregarding the four-coordinated structure, the order of the effectiveionic radius is Co<Fe<Mn in the case of divalent ions, Al<Fe in the caseof trivalent ions, Mn<Cr<Ti in the case of tetravalent ions, and Cr<V inthe case of pentavalent ions. From these results, it is contemplatedthat (Al, Co)<Fe<Mn<Cr<(V, Ti) (the size relationships of the ionicradius between Ti and V or Co and Al cannot be determined). However,since the valences in the data regarding the four-coordinated structureare different from each other, their precise comparison is impossible.Then, referring to the data regarding the six-coordinated structure(i.e., MN₆ octahedron) in which the valences are fixed so as to betrivalent, it is found that the order of the ionic radius isAl<Co<Fe<Mo<Cr<V<Ti (in Table 1, “HS” denotes a high-spin state and “LS”denotes a low-spin state).

The present invention provides an excellent thermistor characteristic bysubstituting the Al site of Al—N, which is an insulator, with Ti or thelake to perform carrier doping, thereby increasing electricconductivity. For example, when the Al site is substituted with Ti, themean ionic radius between Al and Ti increases because the effectiveionic radius of Ti is larger than that of Al. As the result, it isassumed that the atomic distance increases, resulting in the increase ofthe lattice constant.

The increase of the lattice constant by substituting the Al site of Al—Nwith Ti or the like has been confirmed by X-ray data. Per example, inthe X-ray diffraction data described below in the case where “M”=Ti(FIGS. 13 to 23), the peak of (Ti, A)Al—N—O is shifted more to the lowerangle side than the peak of Al—N. From the result, it is found chat thelattice constant of (Ti, A)Al—N—O is larger than that of Al—N. Note thatsince the oxygen (O) is oxygen that compensates nitrogen defects in acrystal or is interstitial oxygen, there is few changes in the latticeconstant. Hence, it is assumed that the change in the lattice constantis not due to the oxygen. In addition to the result described above, thefact that the X-ray diffraction peak corresponding to Al—N is not splitshows that Ti and A are in a solid solution at the Al site. The mainreason why the lattice constant increases in this test is because theincrease of a (M+A)/(M+A+Al) ratio causes the increase of the mean ionicradius because the ionic radius of M, such as Ti, and A is larger thanthat of Al. Note that the substitution amount of M and A in the Al sitein order to maintain the wurzite-type structure has a solubility limit.When (M+A)/(M+A+Al) is larger than 0.3 (i.e., Al/(M+A+Al) becomes lessthan 0.7), a NaCl-type phase tends to be more easily generated than awurtzite-type phase.

In addition, since the ionic radius of V, Cr, Mn, Fe, and Co fallswithin a value between Al and Ti, in view of the lattice constant of thewurzite-type crystal structure, it is contemplated that the substitutionof the Al site with V, Cr, Mn, Fe, or Co not with Ti can suppress theincrease of the lattice constant, when compared by the same substitutionamount, which may allow the wurtzite-type crystal structure to be easilymanaged. Since V, Cr, Mn, Fe, and Co also have a 3d electron(s) and a 4selectron (s) like Ti, carrier doping at the Al site is possible.

Also, the metal nitride material for a thermistor of the presentembodiment is deposited as a film, and is a columnar crystal extendingin a vertical direction with respect to the surface of the film.Furthermore, it is preferable that the metal, nitride material for athermistor is more strongly oriented along the c-axis than the a-axis ina vertical direction with respect to the surface of the film.

Note that the decision about whether a moral nitride material for athermistor has a strong a-axis orientation (100) or a strong c-axisorientation (002) in a vertical direction with respect to the surface orthe film is determined by examining the orientation of the crystal axisusing X-ray diffraction (XPD). When the peak intensity ratio of “thepeak intensity of (100)”/“the peak intensity of (002)”, where (100) isthe hkl index indicating a-axis orientation and (002) is the hkl indexindicating c-axis orientation, is less than 1, the metal nitridematerial for a thermistor is determined to nave a strong c-axisorientation.

Next, a description will be given of a film type thermistor sensor usingthe metal nitride material for a thermistor of the present embodiment.As shown in FIG. 6, a film type thermistor sensor 1 includes aninsulating film 2, a thin film thermistor portion 3 made of the metalnitride material for a thermistor on the insulating film 2, and a pairof pattern electrodes 4 formed at least on the thin film thermistorportion 3.

The insulating film 2 is, for example, a polyimide resin sheet formed ina band shape. The insulating film 2 may foe made of another materialsuch as polyethylene terephthalate (PET), polyethylene naphthalate(PEN), or the like.

The pair of pattern electrodes 4 has a pair of comb shaped electrodeportions 4 a that is patterned so as to have a comb shaped pattern byusing stacked metal films of, for example, a Cr film and an Au film, andis arranged opposite to each, other on the thin film thermistor portion3, and a pair of linear extending portions 4 b extending with the tipends thereof being connected to these comb shaped, electrode portions 4a and the base ends thereof being arranged at the end of the insulatingfilm 2.

A plating portion 4 c such as Au plating is formed as a lead wiredrawing portion on the base end of each of the pair of linear extendingportions 4 b. One end of the lead wire is joined with the platingportion 4 c via a solder material or the like. Furthermore, except forthe end of the insulating film 2 including the plating portions 4 c, apolyimide coverlay film 5 is pressure bonded onto the insulating film 2.Instead of the polyimide coverlay film 5, a polyimide or epoxy-basedresin material layer may be formed onto the insulating film 2 byprinting.

A description will be given below of a method for producing the metalnitride material for a thermistor and a method for producing the filmtype thermistor sensor 1 using the metal nitride material for athermistor with reference to FIG. 7.

Firstly, the method for producing the metal nitride material for athermistor according to the present embodiment includes a depositionstep of performing film deposition by reactive sputtering in a nitrogen-and oxygen-containing atmosphere using an M-A-Al alloy sputtering target(where “M” represents at least one of Ti, V, Cr, Mn, Fe, and Co, and “A”(represents at least one of Sc, Zr, Mo, Nb, and W).

For example, a Ti—Sc—Al alloy sputtering target is employed in the casewhere “M”=Ti, “A”=Sc, a Ti—-Zr—Al alloy sputtering target is employed inthe case where “M”=Ti, “A”=Zr, a Ti—Mo—Al alloy sputtering target isemployed in she case where “M”=Ti, “A”=Mo, a Ti—Nb—Al alloy sputteringtarget is employed in the case where “M”=Ti, “A”=Nb, and a Ti—W—Al alloysputtering target is employed in the case where “M”=Ti, “A”=W.

It is preferable that a spattering gas pressure during the reactivesputtering is set to less titan 1.5 Pa.

Furthermore, it is preferable that the formed film is irradiated withnitrogen plasma after the deposition step.

More specifically, for example, the thin film thermistor portion 3having a thickness of 200 nm, which is made of the metal nitridematerial for a thermistor of the present embodiment, is deposited on theinsulating film 2 which is a polyimide film having a thickness of 50 μmshown in FIG. 7 (a) by the reactive sputtering method as shown in FIG.7(b).

For example, the spattering conditions in the case where “M”=Ti, “A”=Scare as follows: an ultimate degree of vacuum; 5×10⁻⁶ Pa, a sputteringgas pressure; 0.67 Pa, a target input power (output) 300 W, and anitrogen gas partial pressure and an oxygen gas partial pressure under amixed gas (Ar gas+nitrogen gas oxygen gas) atmosphere: 39.8% and 0.2%,respectively.

For example, the sputtering conditions in the case where “M”=Ti, “A”=Zrare as follows: an ultimate degree of vacuum: 5×10⁶ Pa, a sputtering gaspressure: 0.4 Pa, a target input power (output); 300 W and a nitrogengas partial pressure and an oxygen gas partial pressure trader a mixedgas (Ar gas+nitrogen gas+oxygen gas) atmosphere: 19.8% and 0.2%,respectively.

For example, the sputtering conditions in she case where “M”=Ti, “A”=Moare as follows: an ultimate degree or vacuum: 5/10⁻⁶ Pa, a sputteringgas pressure: 0.4 Pa, a target input power (output): 300 W, and anitrogen gas partial pressure and an oxygen gas partial pressure under amixed gas (Ar gas+nitrogen gas+oxygen gas) atmosphere: 39.8% and 0.2%,respectively.

For example, the sputtering conditions in the case where “M”=Ti, “A”=Ware as follows: an ultimate degree of vacuum: 5×10⁻⁶ Pa, a sputteringgas pressure: 0.4 Pa, a target input power (output): 300 W, and anitrogen gas partial pressure and an oxygen gas partial pressure under amixed gas (Ar gas e nitrogen gas e oxygen gas) atmosphere: 19.8% and0.2%, respectively.

For example, the sputtering conditions in the case where “M”=Ti, “A”=Ware as follows: an ultimate degree of vacuum: 5×10⁻⁶ Pa sputtering gaspressure: 0.4 Pa, a target input power, (output): 300 W and a nitrogengas partial pressure and an oxygen gas partial pressure under a mixedgas (Ar gas+nitrogen gas+oxygen gas) atmosphere: 19.8% and 0.2%,respectively.

The metal nitride material for a thermistor having a desired size isdeposited on the insulating film 2 using a metal mask so as to form thethin film thermistor portion 3. It is preferable that, the formed thinfilm thermistor portion 3 is irradiated with nitrogen plasma. Forexample, the thin film thermistor portion 3 is irradiated with nitrogenplasma under the degree of vacuum of 6.7 Pa, the output of 200 W, andthe N₂ gas atmosphere.

Next, a Cr film having a thickness of 20 nm is formed and an Au filmhaving a thickness of 200 nm is further formed thereon by the sputteringmethod, furthermore, a resist solution is coated on the stacked metalfilms using a barcoater, and then pre-baking is performed for 1.5minutes at a temperature of 110° C. After being exposed by an exposuredevice, any unnecessary portion is removed by a developing solution, andthen patterning is performed by post-baking for 5 minutes at atemperature of 150° C. Then, any unnecessary electrode portion issubject to wet etching using commercially available Au enchant and Cretchant, and then the resist is stripped as shown in FIG. 7(c) so as toform a pair of the pattern electrodes 4 each having a desired combshaped electrode portion 4 a. More that the pattern electrodes 4 may beformed in advance on the insulating film 2, and then the thin filmthermistor portion may be deposited on the comb shaped electrodeportions 4 a. In this case, the comb shaped electrode portions 4 a ofthe pattern electrodes 4 are formed below the thin film thermistorportion 3.

Next, as shown in FIG. 7(d), for example, the polyimide coverlay film 5with an adhesive having a thickness of 50 μm is placed on. theinsulating film 2, and then they are bonded to each other underpressurization of 2 MPa at a temperature of 150° C. for 10 minutes usinga press machine. Furthermore, as shown in FIG. 7(e), an Au thin filmhaving a thickness of 2 μm is formed at the base ends of the linearextending portions 4 b using an Au plating solution so as to form theplating portions 4 c.

When a plurality of film type thermistor, sensors 1 is simultaneouslyproduced, a plurality of thin film thermistor portions 3 and a pluralityof pattern electrodes 4 are formed on a large-format sheet of theinsulating film 2 as described above, and then, the resultinglarge-format, sheet, is cut into a plurality of segments so as to obtaina plurality of film type thermistor sensors 1.

In this manner, a thin film type thermistor sensor 1 having a size of25×3.6 mm arid a thickness of 0.1 mm is obtained.

As described above, since the metal nitride material for a thermistor orthe present embodiment consists of a metal nitride represented by thegeneral formula: (M_(1-v)A_(v))_(x)Al_(y)(N_(1-w)O_(w))_(z) ( where “M”represents at least one of Ti, V, Cr, Mn, Fe, and Co, “A” represents atleast one of Sc, Zr, Mo, Nb, and W, 0.0<v<1.0, 0.70≦y/(x+y) ≦0.98,0.45≦z≦0.55, 0<w≦0.35, and x+y+z=1), wherein the crystal structurethereof is a hexagonal wurtzite-type (space group: P6₃mc (No. 186)single phase, a good B constant and an excellent heat resistance can beobtained without firing. In particular, the heat resistance can befurther improved by the effect of oxygen (O) included in a crystal so asto compensate nitrogen defects in the crystal or the like.

Since the metal nitride material for a thermistor is a columnar crystalextending in a vertical direction with respect to the surface of thefilm, the crystallinity of the film is high, so tear high heatresistance can be obtained.

Furthermore, since the metal nitride material for a thermistor is morestrongly oriented along the c-axis than the a-axis in a verticaldirection with respect to the surface of the film, a high E constant ascompared with the case of a strong a-axis orientation can be obtained.

Since, in the method for producing the metal nitride material for athermistor of the present embodiment, film deposition is performed byreactive sputtering in a nitrogen- and oxygen-containing atmosphereusing an M-A-Al (where “M” represents at least one of Ti, V, Cr, Mn, Fe,and Co, arid “A” represents at least one of Sc, Zr, Mo, Nb, and W) alloysputtering target, the metal nitride material for a thermistor, whichconsists of a metal nitride represented by the aforementioned generalformula: (M, A)_(x)Al_(y)(N, O)_(z), can be deposited on a film withoutfiring.

Thus, since, in the film type thermistor sensor 1 using the metalnitride material for a thermistor of the present embodiment, the thinfilm thermistor portion 3 made of the metal nitride material for athermistor is formed on the insulating film 2, the insulating film 2having low heat resistance, such as a resin film, can be used becausethe thin film thermistor portion 3 is formed without firing and has ahigh B constant are; high heat resistance, so that a thin and flexiblethermistor sensor having an excellent thermistor characteristic can beobtained.

A substrate material using a ceramic such as alumina that has often beenconventionally used has a problem that if the substrate material isthinned to a thickness of 0.1 mm, for example, the substrate material isvery fragile and breaks easily. On the order hand, since a film can beused in the present embodiment, a very thin film, type thermistor sensorhaving a thickness of 0.1 mm, for example, can be provided.

EXAMPLES

Next, the evaluation results of the materials according to Examplesproduced based on the above embodiment regarding the metal nitridematerial for a thermistor, a method for producing the same, and a filmtype thermistor sensor according to the present invention will bespecifically described with reference to FIGS. 8 to 28.

<Production of Film Evaluation Element>

The film evaluation elements 121 shown in FIG. 8 were produced inExamples and Comparative Examples of the present invention. In each ofthe following Examples of the present invention, the film evaluationelements 121 were produced using a(Ti_(1-v)Sc_(v))_(x)Al_(y)(N_(1-w)O_(w))_(z) metal nitride for athermistor in the case where “M”=Ti, “A”=Sc, a(Ti_(1-v)Zr_(v))_(x)Al_(y)(N_(1-w)O_(w))_(x) metal nitride for athermistor in the case where “M”=Ti, “A”=Zr, a(Ti_(1-v)Mo_(v))_(x)Al_(y)(N_(1-w)O_(z) metal nitride for a thermistorin the case where “M”=Ti, “A”=Mo, a(Ti_(1-v)Nb_(v))_(x)Al_(y)(N_(1-w)O_(w))_(z) metal nitride for athermistor in the case where “M”=Ti, “A”=Nb, a(Ti_(1-v)W_(v))_(x)Al_(y)(N_(1-u)O_(u))_(z) metal nitride for athermistor in the case where “M”=Ti, “A”=W, a(Cr_(1-v)Zr_(v))_(x)Al_(y)(N_(1-w)O_(w))_(z) metal nitride for athermistor in the case where “M”=Cr, “A”=Zr, a(Cr_(1-v)Mo_(v))_(x)Al_(y)(N_(1-w)O_(w))_(z) metal nitride for athermistor in the case where “M”=Cr, “A”=Mo, a(Cr_(1-v)Nb_(v))_(x)Al_(y)(N_(1-w)O_(w))_(z) metal nitride for athermistor in the case where “M”=Cr, “A”=Nb, and a(Cr_(1-v)W_(v))_(x)Al_(y)(N_(1-u)O_(u))_(z) metal nitride for athermistor in the case where “M”=Cr, “A”=W.

Firstly, each of the thin film thermistor portions 3 hawing a thicknessof 500 nm, which were made of the metal nitride materials for athermistor with the various composition ratios shown in Tables 2 to 7,was formed on an Si wafer with a thermal oxidation film as an Sisubstrate S by using a Ti—Sc—Al alloy target, a Ti—Zr—Al alloy target, aTi—Mo—Al alloy target, a Ti—Nb—Al alloy target, a Ti—d—Al alloy target,a Cr—Zr—Al alloy target, a Cr—Nb—Al alloy target, a Cr—Mo—Al alloytarget, or a Cr—W—Al alloy target with various composition ratios by thereactive sputtering method. The thin film thermistor portions 3 wereformed under the sputtering conditions of an ultimate degree of vacuumof 5×10⁻⁶ Pa, a sputtering gas pressure of from 0.1 to 1 Pa, a targetinput power (output) of from 100 to 500 W, and a nitrogen gas partialpressure and an oxygen gas partial pressure under a mixed gas (Argas+nitrogen gas+oxygen gas) atmosphere of from 10 to 100% and from 0 to3%, respectively.

Next, a Cr film having a thickness of 20 nm was formed and an Au filmhaving a thickness of 200 nm was further formed on each of the thin filmthermistor portions 3 by the sputtering method. Furthermore, a resistsolution was coated on the stacked metal films using a spin coater, andthen pre-baking was performed for 1.5 minutes at a temperature of 110°C. After being exposed by an exposure device, any unnecessary portionwas removed by a developing solution, and then patterning was performedby post-baking for 5 minutes at a temperature of 150° C. Then, anyunnecessary electrode portion was subject to wet etching usingcommercially available Au etchant and Cr etchant, and then the resistwas stripped so as to form a pair of pattern electrodes 124, each havinga desired comb shaped electrode portion 124 a. Then, the resultantelements were diced into chip elements so as to obtain film evaluationelements 121 used for evaluating a B constant and for testing heatresistance.

Note that the film evaluation elements 121 according to ComparativeExamples, each having the composition ratio of (M, A)_(x)Al_(y)(N,O)_(z) (where “M” represents at least one of Ti, V, Cr, Mn, Fe, and Co,and “A” represents at least one of Sc, Zr, Mo, Nb, and W) outside therange of the present invention, and have different crystal systems, weresimilarly produced for comparative evaluation.

<Film Evaluation>

(1) Composition Analysis

Elemental analysis was performed, on the thin film thermistor portions 3obtained by the reactive sputtering method by X-ray photoelectronspectroscopy (XPS). In the XPS, a quantitative analysis was performed ona sputtering surface at a depth of 20 nm from the outermost surface byAr sputtering. The results are sheen in Tables 2 to 7. In the followingtables, the composition ratios are expressed by “at %”. Some of tinesamples were also subject to a quantitative analysis for a sputteringsurface at a depth of 100 nm from the outermost surface to confirm thatit had the same composition within the quantitative accuracy as one inthe sputtering surface at a depth of 20 nm.

In the X-ray photoelectron spectroscopy (XPS), a quantitative analysiswas performed under the conditions of an X-ray source of MgKα (350 W), apath energy of 58.0 eV, a measurement interval of 0.125 eV, aphoto-electron take-off angle with respect to a sample surface of 45deg, and an analysis area of about 800 μmφ. Note that the quantitativeaccuracy of N/(M+A+Al+N+O) and O/(M+A+Al+N+O) was ±2%, arid that ofAl/(M+A+Al) was ±1, respectively (where “M” represents at least one ofTi, V, Cr, Mn, Fe, and Co, and “A” represents at least one of Sc, Zr,Mo, Nb, and W).

(2) Specific Resistance Measurement

The specific resistance, of each of the thin film thermistor portions 3obtained by the reactive spattering method was measured by thefour-probe method at a temperature of 25° C. The results are shown inTables 2 to 7.

(3) Measurement of B Constant

The resistance values for each of the film evaluation elements 121 attemperatures of 25° C. and 50° C. were measured in a constant,temperature bath, and a B constant was calculated based on theresistance values at temperatures of 25° C. and 50° C. The results areshown in Tables 2 to 7. In addition, it was confirmed that the filmevaluation elements 121 were thermistors having a negative temperaturecharacteristic by the resistance values at temperatures of 25° C. and50° C.

In the B constant calculating method of the present invention, a Bconstant is calculated by the following formula using the resistancevalues at temperatures of 25° C. and 50° C.

B constant (K)=In(R25/R50)/(1/T25-1/T50)

R25 (Ω): resistance value at 25° C.

R50 (Ω): resistance value at 50° C.

T25 (K): 298.15 K, which is an absolute temperature of 25° C. expressedin Kelvin

T50 (K): 323.15 K, which is an absolute temperature of 50° C. expressedin Kelvin

As can be seen from these results, a thermistor characteristic having aresistivity of 250 Ωcm or higher and a B constant of 1500 K or higher isachieved in all of the Examples in which the composition ratios of (M,A)_(x)Al_(y)(N, O)_(z) (where “M” represents at least, one of Ti, V, Cr,Mn, Fe, and Co, “A” represents at least one of Sc, Zr, Mo, Nb, and W)fall within the region enclosed by the points A, B, C, and D in theternary phase diagrams shown in FIGS. 1 to 5, i.e., the region where“0.0<v<1.0, 0.70≦y/(x+y)≦0.98, 0.45≦z≦0.55, 0<w≦0.35, and x+y+z=1”.

Graphs illustrating the relationships between a resistivity at 25° C.and a B constant from the above results are shown la FIGS. 9 to 13. Agraph illustrating the relationship between the Al/(Ti+Sc+Al) ratio andthe B constant is also shown in FIG. 14. A graph illustrating therelationship between the Al/(Ti+Zr+Al) ratio and the B constant is alsoshown in FIG. 15. A graph illustrating the relationship between theAl/(Ti+Mo+Al) ratio and the B constant is also shown in FIG. 16. A graphillustrating the relationship between the Al/(Ti+Mo+Al) ratio and the Bconstant is also shown in FIG. 17. Further, a graph illustrating therelationship between the Al/(Ti+W+Al) ratio and the B constant is alsoshown in FIG. 18.

From these graphs, the film evaluation elements 121, the compositionratios of which fall within the region where Al/(Ti+Sc+Al) is from 0.7to 0.98 and N+O/(Ti+Sc+Al+N+O) is from 0.45 to 0.55 and each crystalsystem of which is a hexagonal wurtzite-type single phase, have aspecific resistance value at a temperature of 25° C. of 250 Ωcm orhigher and a B constant of 1500 K or higher, which are the regionsrealizing a high resistance and a high B constant.

The film evaluation elements 121, the composition ratios of which fallwithin the region where Al/(Ti+Zr+Al) is from 0.7 to 0.98 andN+O/(Ti—Zr—Al+N+O) is from 0.45 to 0.55 and each crystal system: ofwhich is a hexagonal wurtzite-type single phase, also have a specificresistance value at a temperature of 25° C. of 250 Ωcm or higher and a Bconstant of 1500 K or higher, which are the regions realizing a highresistance and a high B constant.

The film evaluation elements 121, the composition ratios of which fallwithin the region where Al/(Ti+Mo+Al) is from 0.7 to 0.98 andN+O/(Ti+Mo+Al+N+O) is from 0.45 to 0.55 and each crystal system of whichis a hexagonal wurtzite-type single phase, also have a specificresistance value at a temperature of 25° C. of 250 Ωcm or higher and a Bconstant of 1500 K or higher, which are the regions realizing a highresistance and a high B constant.

The film evaluation elements 121, the composition ratios of which fallwithin the region where Al/(Ti+Nb+Al) is from 0.7 to 0.98 andN+O/(ti+Nb+Al+N+O) is from 0.45 to 0.55 and each; crystal system ofwhich is a hexagonal wurtzite-type single phase, also have a specificresistance value at a temperature of 25° C. of 250 Ωcm or higher and a Bconstant of 1500 K or higher, which are the regions realizing a highresistance and a high B constant.

Furthermore, the film evaluation elements 121 the composition ratios ofwhich rail within the region where Al/(Ti+W+Al) is from 0.7 to 0.98 andN+O/(Ti+W+Al+N+O) is from 0.45 to 0.55 and each crystal system of whichis a hexagonal wurtzite-type single phase also have a specificresistance value at a temperature of 25° C. of 250 Ωcm or higher and a Bconstant of 1500 K or higher, which are the regions realizing a highresistance and a high B constant.

In data shown in FIGS. 14 to 18, the reason why the B constant varieswith respect to nearly the same Al/(Ti+Sc+Al) ratio, Al/(Ti+Zr+Al)ratio, Al/(Ti+Mo+Al) ratio, Al/(Ti+Nb+Al) ratio, or Al/(Ti+W+Al) ratiois because the film evaluation elements 121 have different amounts ofnitrogen and/or oxygen in their crystals or different amounts of latticedefects such as nitrogen and/or oxygen defects.

In the material according to Comparative Example 2, where “M”=Ti,“A”=Sc, as shown in Table 2, the composition ratio falls within theregion where Al/(Ti+Sc+Al)<0.7, and the crystal system is a cubicNaCl-type phase. Thus, a material with the composition that falls withinthe region where Al/(Ti+Sc+Al)<0.7 has a specific resistance value at atemperature of 25° C. of less than 250 Ωcm and a B constant of less than1500 K, which are the regions of low resistance and low B constant.

In the material according to Comparative Example 1 shown in Table 2, thecomposition ratio falls within the region where N+O/(Ti+Sc+Al+N+O) isless than 40%, that is, the material is in a crystal state wherenitridation of metals contained therein is insufficient. Tee materialaccording to Comparative Example 1 was neither a NaCl-type norwurzite-type phase and had very poor crystallinity. In addition, it wasfound that the material according to this Comparative Example exhibitednear-metallic behavior because both the B constant and the resistancevalue were very small.

In the material according to Comparative Example 2, where “M”=Ti,“A”=Zr, as shown in Table 3, the composition ratio falls within theregion where Al/(Ti+Zr+Al)<0.7, and the crystal system is a cubicNaCl-type phase. Thus, a material with the composition that falls withinthe region where Al/(Ti+Zr+Al)<0.7 has a specific resistance value at atemperature of 25° C. of less than 250 Ωcm and a B constant of less than1500 K, which are the regions of low resistance and low B constant.

In the material according to Comparative Example 1 shown in Table 3, thecomposition ratio fails within the region where N+O/(ti+Zr+Al+N+) isless than 40%, that is, the material is in a crystal state wherenitridation of metals contained therein is insufficient. The materialaccording to comparative Example 1 was neither a NaCl-type norwurtzite-type phase and had very poor crystallinity. In addition, it wasfound that the material according to this Comparative Example exhibitednear-metallic behavior because both the B constant, and the resistancevalue were very small.

In the material according to Comparative Example 2, where “M”Ti, “A”=Mo,as shown in Table 4. the composition ratio falls within the region whereAl/(Ti+Mo+Al<0.66, and the crystal system is a cubic NaCl-type phase. Inthe material according to Comparative Example 3 shown in Table 4, thecomposition ratio falls within the region where 0.66<Al/(Ti+Mo+Al)<0.70,and the crystal system is two coexisting phases of a NaCl-type phase anda wurtzite-type phase. Thus, a material with, the composition that fallswithin the region where Al/(Ti+Mo+Al)<0.7 has a specific resistancevalue at a temperature of 25° by of less than 250 Ωcm and a B constantof less than 1500 K, which are the regions of low resistance and low Bconstant. In the material according to Comparative Example 1 shown inTable 4, the composition ratio falls within the region whereN+O(Ti+Mo+Al+N+O) is less than 40%, that is, the material is in acrystal state where nitridation of metals contained therein isinsufficient. The material according to Comparative Example 1 wasneither a NaCl-type nor wurtzite-type phase and had very poorcrystallinity. In addition, it was found that the material according tothis Comparative Example exhibited near-metallic behavior because boththe B constant and the resistance value were very small.

In the material according to Comparative Example 2, where “M”=Ti,“A”=Nb, as shown in Table 5, the composition ratio falls within theregion where Al/(Ti+Nb+Al)<0.7, and the crystal system is a cubicNaCl-type phase. Thus, a material with, the composition that fallswithin the region where Al/(Ti+Nb+Al)<0.7 has a specific resistancevalue at a temperature of 25° C. of less than 250 Ωcm and a B constantof less than 1500 K, which are the regions of low resistance and low Bconstant.

In the material according to Comparative Example 1 shown in Table 5, thecomposition ratio falls within the region, where N+O/(Ti+Nb+Al+N+O) isless than 40%, that is, the material is in a crystal state wherenitridation of metals contained therein is insufficient. The materialaccording to Comparative Example 1 was neither a NaCl-type norwurtzite-type phase and had very poor crystallinity. In addition, it wasfound that the material according to this Comparative Example exhibitednear-metallic behavior because both the B constant and the resistancevalue were very small.

In the material according to Comparative Example 2, where “M”=Ti, “A”=W,as shown in Table 6, the composition ratio falls within the region whereAl/(Ti+W+Al)<0.7, and the crystal system is a cubic NaCl-type phase.Thus, a material with the composition that falls within the region whereAl/(Ti+W+Al)<0.7 has a specific resistance value at a temperature of 25°C. of less than 250 Ωcm and a B constant of less than 1500 K, which arethe regions of low resistance and low B constant.

In the material according to Comparative Example 1 shown in Table 6, thecomposition ratio falls within the region where N+O/(Ti+W+Al+N+O) isless than 40%, and thus, the material is in a crystal state wherenitridation of metals contained therein is insufficient. The materialaccording to Comparative Example 1 was neither a NaCl-type norwurtzite-type phase and had very poor crystallinity. In addition, it wasfound that the material according to this Comparative Example exhibitednear-metallic behavior because both the B constant and the resistancevalue were very small.

Note that, even in the materials according to the Examples shown inTable 7, where “M” is Cr and “T” is Zr, Nb, Mo, or W, when Al/(Cr A+Al)is from 0.7 to 0.98 and N+O/(Cr+A+Al+N+O) is from 0.45 to 0.55, awurtzite-type hexagonal crystal having thermistor characteristic of highresistance and high B constant can be obtained.

4) Thin Film X-Ray Diffraction (Identification of Crystal Phase)

The crystal phases of the thin film thermistor portions 3 obtained bythe reactive sputtering method were identified by Grazing incidenceX-ray Diffraction. The thin film X-ray diffraction is a small angleX-ray diffraction experiment. The measurement was performed under theconditions of a vessel of Cu, the angle of incidence of 1 degree, and 20of from 20 to 130 degrees. Some of the samples were measured under thecondition of the angle of incidence of 0 degree and 2θ of from 20 to 100degrees.

As a result, of the measurement, a wurtzite-type phase (hexagonal, thesame phase as that of Al—N) was obtained in the region whereAl/(M+A+Al)≧0.7 (where “M” represents at least one of Ti, V, Cr, Mn, Fe,and Co, and “A” represents at least one of Sc, Zr, Mo, Nb, and W),whereas a NaCl-type phase (cubic, the same phase as that of TiN, ScN,ZrN, MoN, and NbN) was obtained in the region where Al/(M+A+Al)<0.66. Itis also contemplated that a crystal phase in which a wurtzite-type phaseand a NaCl-type phase coexist will be obtained in the region where0.66<Al/(M+A+Al)<0.7.

Thus, in the (M, A)_(x)Al_(y)(N, O)_(z)-based material (where “M”represents at least one of Ti, V, Cr, Mn, Fe, and Co, and “A” representsat least one of Sc, Zr, Mo, Nb, and W), the regions of high resistanceand high B constant can be realized by the wurtzite-type phase having aratio of Al/(M+A+Al)>0.7. In the Examples of the present invention; noimpurity phase was confirmed and the crystal structure thereof was awurtzite-type single phase.

In Comparative Example 1 shown in Tables 2 to 6, the crystal phasethereof was neither a wurtzite-type nor NaCl-type phase as describedabove, and thus, could not be identified in the testing. In thisComparative Example, the peak width of XRD was very large, showing thatthe material had very poor crystallinity. It is contemplated that thecrystal phase thereof was metal phase with insufficient nitridation andinsufficient oxidation because it exhibited near-metallic behavior fromthe viewpoint of electric characteristics.

TABLE 2 CRYSTAL AXIS EXHIBITING STRONG DEGREE OF ORIENTATION XRD PEAK INVERTICAL INTENSITY DIRECTION RESULT OF RATIO OF WITH RESPECT ELECTRIC(100)/(002) TO SUBSTRATE SPUT- COMPOSITION RATIO PROPERTIES WHEN SURFACEWHEN TERING Ti/(Ti + Sc/(Ti + Al/(Ti + N/(Ti + O/(Ti + Al/ (N + O)/SPECIFIC CRYSTAL CRYSTAL PHASE GAS Sc + Sc + Sc + Sc + Sc + (Ti + (Ti +Sc + N/ RESISTANCE PHASE IS IS WURTZITE PRES- Al + Al + Al + Al + Al +Sc + Sc/ Al + (Ti + Sc + O/ B CON- VALUE CRYSTAL WURTZITE TYPE (c-AXISSURE N + O) N + O) N + O) N + O) N + O) Al) (Ti + Sc) N + O) Al + N)(N + O) STANT AT 25° C. SYSTEM TYPE OR a-AXIS) (Pa) (%) (%) (%) (%) (%)(%) (%) (%) (%) (%) (K) (Ω cm) COMPAR- UNKNOWN — — — 14.4 0.2 51 30 5 781.3 35 31 14 61 5.E+00 ATIVE (INSUFFICIENT EXAMPLE 1 NITRIDATION)COMPAR- NaCl TYPE — — — 17.9 0.2 32 44 6 64 1.1 50 47 13 345 5.E+01ATIVE EXAMPLE 2 EXAMPLE 1 WURTZITE 0.05 c-AXIS <1.5 12.2 0.2 37 47 4 751.4 51 48 8 1887 1.E+04 TYPE EXAMPLE 2 WURTZITE 0.09 c-AXIS <1.5 9.0 0.138 47 6 81 0.9 53 50 11 2238 2.E+05 TYPE EXAMPLE 3 WURTZITE 0.83 c-AXIS<1.5 2.9 0.1 46 44 7 94 2.3 51 48 13 4220 6.E+07 TYPE EXAMPLE 4 WURTZITE1.10 a-AXIS <1.5 4.0 0.3 48 40 8 92 6.3 48 43 17 3620 8.E+07 TYPEEXAMPLE 5 WURTZITE 1.32 a-AXIS <1.5 10.7 0.3 36 35 18 77 2.5 53 42 351782 2.E+04 TYPE EXAMPLE 6 WURTZITE 1.36 a-AXIS <1.5 9.1 0.2 42 45 4 822.3 49 47 9 2015 1.E+05 TYPE EXAMPLE 7 WURTZITE 2.36 a-AXIS <1.5 8.3 0.842 43 6 82 8.9 49 46 13 1893 3.E+05 TYPE

TABLE 3 CRYSTAL AXIS EXHIBITING STRONG DEGREE OF ORIENTATION XRD PEAK INVERTICAL INTENSITY DIRECTION RESULT OF RATIO OF WITH RESPECT ELECTRIC(100)/(002) TO SUBSTRATE SPUT- COMPOSITION RATIO PROPERTIES WHEN SURFACEWHEN TERING Ti/(Ti + Zr/(Ti + Al/(Ti + N/(Ti + O/(Ti + Al/ (N + O)/SPECIFIC CRYSTAL CRYSTAL PHASE GAS Zr + Zr + Zr + Zr + Zr + (Ti + (Ti +Zr + N/ RESISTANCE PHASE IS IS WURTZITE PRES- Al + Al + Al + Al + Al +Zr + Zr/ Al + (Ti + Zr + O/ B CON- VALUE CRYSTAL WURTZITE TYPE (c-AXISSURE N + O) N + O) N + O) N + O) N + O) Al) (Ti + Zr) N + O) Al + N)(N + O) STANT AT 25° C. SYSTEM TYPE OR a-AXIS) (Pa) (%) (%) (%) (%) (%)(%) (%) (%) (%) (%) (K) (Ω cm) COMPAR- UNKNOWN — — — 14 4 49 24 9 74 2133 26 28 188 8.E−02 ATIVE (INSUFFICIENT EXAMPLE NITRIDATION) 1 COMPAR-NaCl TYPE — — — 18 2 31 43 6 61 10 49 46 13 224 7.E+00 ATIVE EXAMPLE 2EXAMPLE 1 WURTZITE 0.41 c-AXIS <1.5 9 2 36 43 10 76 17 53 48 19 24626.E+03 TYPE EXAMPLE 2 WURTZITE 0.66 c-AXIS <1.5 12 2 38 41 7 74 11 48 4414 1625 3.E+04 TYPE EXAMPLE 3 WURTZITE 0.07 c-AXIS <1.5 6 1 42 46 5 8516 51 48 11 2588 3.E+03 TYPE EXAMPLE 4 WURTZITE 0.05 c-AXIS <1.5 6 2 4146 5 84 24 51 48 10 2771 9.E+03 TYPE EXAMPLE 5 WURTZITE 0.47 c-AXIS <1.53 1 48 43 5 93 26 48 46 10 5502 2.E+06 TYPE EXAMPLE 6 WURTZITE 2.05a-AXIS <1.5 2 1 44 39 14 93 31 53 45 26 5245 2.E+06 TYPE

TABLE 4 CRYSTAL AXIS EXHIBITING STRONG DEGREE OF ORIENTATION XRD PEAK INVERTICAL INTENSITY DIRECTION RESULT OF RATIO OF WITH RESPECT ELECTRIC(100)/(002) TO SUBSTRATE SPUT- COMPOSITION RATIO PROPERTIES WHEN SURFACEWHEN TERING Ti/(Ti + Mo/(Ti + Al/(Ti + N/(Ti + O/(Ti + (N + O)/ SPECIFICCRYSTAL CRYSTAL PHASE GAS Mo + Mo + Mo + Mo + Mo + Al/(Ti + (Ti + N/RESISTANCE PHASE IS IS WURTZITE PRES- Al + Al + Al + Al + Al + Mo + Mo/Mo +Al + (Ti + Mo + O/ B CON- VALUE CRYSTAL WURTZITE TYPE (c-AXIS SUREN + O) N + O) N + O) N + O) N + O) Al) (Ti +Mo) N + O) Al + N) (N + O)STANT AT 25° C. SYSTEM TYPE OR a-AXIS) (Pa) (%) (%) (%) (%) (%) (%) (%)(%) (%) (%) (K) (Ω cm) COMPAR- UNKNOWN — — — 16 4 57 16 7 74 21 22 232.E+01 ATIVE (INSUFFICIENT EXAMPLE 1 NITRIDATION) COMPAR- NaCl TYPE — —— 17 2 30 42 9 61 8 51 250 1.E+02 ATIVE EXAMPLE 2 COMPAR- NaCl TYPE + —— — 9 8 38 34 11 69 47 45 1288 2.E+02 ATIVE WURTZITE EXAMPLE 3 TYPEEXAMPLE 1 WURTZITE 0.72 c-AXIS <1.5 5 6 41 43 5 78 56 48 45 10 25702.E+03 TYPE EXAMPLE 2 WURTZITE 0.10 c-AXIS <1.5 3 0.5 49 45 2 93 15 4746 4 4550 1.E+07 TYPE EXAMPLE 3 WURTZITE 0.72 c-AXIS <1.5 7 5 43 40 5 8041 45 42 12 2608 5.E+04 TYPE EXAMPLE 4 WURTZITE 1.10 a-AXIS <1.5 3 0.346 36 15 93 9 50 42 29 3868 2.E+06 TYPE EXAMPLE 5 WURTZITE 4.94 a-AXIS<1.5 8 5 37 37 13 74 41 50 42 26 2446 3.E+03 TYPE

TABLE 5 CRYSTAL AXIS EXHIBITING STRONG DEGREE OF ORIENTATION XRD PEAK INVERTICAL INTENSITY DIRECTION RESULT OF RATIO OF WITH RESPECT ELECTRIC(100)/(002) TO SUBSTRATE SPUT- COMPOSITION RATIO PROPERTIES WHEN SURFACEWHEN TERING Ti/(Ti + Mo/(Ti + Al/(Ti + N/(Ti + O/(Ti + (N + O)/ SPECIFICCRYSTAL CRYSTAL PHASE GAS Mo + Mo + Mo + Mo + Mo + Al/(Ti + (Ti +Mo + N/RESISTANCE PHASE IS IS WURTZITE PRES- Al + Al + Al + Al + Al + Mo + Mo/Al + (Ti + Mo + O/ B CON- VALUE CRYSTAL WURTZITE TYPE (c-AXIS SURE N +O) N + O) N + O) N + O) N + O) Al) (Ti +Mo) N + O) Al + N) (N + O) STANTAT 25° C. SYSTEM TYPE OR a-AXIS) (Pa) (%) (%) (%) (%) (%) (%) (%) (%)(%) (%) (K) (Ω cm) COMPAR- UNKNOWN — — — 17 3 56 22 2 74 15 23 22 8 346.E−02 ATIVE (INSUFFICIENT EXAMPLE 1 NITRIDATION) COMPAR- NaCl TYPE — —— 17 2 30 42 9 61 11 51 46 18 381 6.E−01 ATIVE EXAMPLE 3 EXAMPLE 1WURTZITE 0.03 c-AXIS <1.5 6 2 42 48 2 83 27 50 49 4 2549 6.E+02 TYPEEXAMPLE 2 WURTZITE 0.02 c-AXIS <1.5 5 2 42 46 5 85 26 50 48 8 28731.E+04 TYPE EXAMPLE 3 WURTZITE 0.10 c-AXIS <1.5 2 1 48 44 5 93 33 48 4610 4252 1.E+06 TYPE EXAMPLE 4 WURTZITE 0.30 c-AXIS <1.5 10 1 36 44 9 7612 52 48 16 2298 5.E+04 TYPE EXAMPLE 5 WURTZITE 0.87 c-AXIS <1.5 12 2 3942 5 75 11 47 45 10 1812 3.E+02 TYPE EXAMPLE 6 WURTZITE 2.78 a-AXIS <1.56 2 41 37 14 84 28 51 43 27 2384 6.E+03 TYPE EXAMPLE 7 WURTZITE 2.56a-AXIS <1.5 2 2 45 38 13 92 43 51 44 26 3523 3.E+05 TYPE

TABLE 6 CRYSTAL AXIS EXHIBITING STRONG DEGREE OF ORIENTATION XRD PEAK INVERTICAL INTENSITY DIRECTION RESULT OF RATIO OF WITH RESPECT ELECTRIC(100)/(002) TO SUBSTRATE SPUT- COMPOSITION RATIO PROPERTIES WHEN SURFACEWHEN TERING Ti/(Ti + W/(Ti + (N + O)/ SPECIFIC CRYSTAL CRYSTAL PHASE GASW + W + Al/(Ti + N/(Ti + O/(Ti + (Ti + W + N/ RESISTANCE PHASE IS ISWURTZITE PRES- Al + Al + W + Al + W + Al + W + Al + Al/(Ti + W/(Ti +Al + (Ti + W + O/ B CON- VALUE CRYSTAL WURTZITE TYPE (c-AXIS SURE N + O)N + O) N + O) N + O) N + O) W + Al) W) N + O) Al + N) (N + O) STANT AT25° C. SYSTEM TYPE OR a-AXIS) (Pa) (%) (%) (%) (%) (%) (%) (%) (%) (%)(%) (K) (Ω cm) COMPAR- UNKNOWN — — — 4 1 76 14 5 94 10 19 15 25 538.E−01 ATIVE (INSUFFICIENT EXAMPLE 1 NITRIDATION) COMPAR- NaCl TYPE — —— 17 3 32 43 5 61 15 48 45 10 469 3.E+00 ATIVE EXAMPLE 3 EXAMPLE 1WURTZITE 0.01 c-AXIS <1.5 6 6 39 46 3 76 53 49 47 6 2454 2.E+03 TYPEEXAMPLE 2 WURTZITE 0.01 c-AXIS <1.5 6 8 39 43 4 73 55 47 45 8 23001.E+03 TYPE EXAMPLE 3 WURTZITE 0.48 c-AXIS <1.5 3 1 49 44 3 92 14 47 466 3350 2.E+06 TYPE EXAMPLE 4 WURTZITE 1.41 a-AXIS <1.5 3 0.4 46 39 12 9312 50 44 23 2950 3.E+05 TYPE EXAMPLE 5 WURTZITE 1.35 a-AXIS <1.5 5 7 3842 8 76 54 50 46 17 1810 6.E+02 TYPE

TABLE 7 CRYSTAL AXIS EXHIBITING STRONG DEGREE OF ORIENTATION XRD PEAK INVERTICAL INTENSITY DIRECTION RATIO OF WITH RESPECT COMPOSITION RATIO(100)/(002) TO SUBSTRATE SPUT- M/ A/ Al/ N/ WHEN SURFACE WHEN TERING(M + (M + (M + (M + CRYSTAL CRYSTAL PHASE GAS A + A + A + A + PHASE ISIS WURTZITE PRES- Al + Al + Al + Al + CRYSTAL WURTZITE TYPE (c-AXIS SUREM A N + O) N + O) N + O) N + O) SYSTEM TYPE OR a-AXIS) (Pa) ELEMENTELEMENT (%) (%) (%) (%) EXAMPLE 1 WURTZITE 0.04 c-AXIS <1.5 Cr Zr 3 4 4240 TYPE EXAMPLE 2 WURTZITE <0.01 c-AXIS <1.5 Cr Nb 0.4 4 46 44 TYPEEXAMPLE 3 WURTZITE <0.01 c-AXIS <1.5 Cr Nb 0.2 4 46 45 TYPE EXAMPLE 4WURTZITE 0.07 c-AXIS <1.5 Cr Mo 3 5 42 38 TYPE EXAMPLE 5 WURTZITE 0.07c-AXIS <1.5 Cr W 4 5 42 37 TYPE RESULT OF ELECTRIC PROPERTIESCOMPOSITION RATIO SPECIFIC O/ (N + O)/ RESIS- (M + Al/ (M + TANCE A +(M + A/ A + N/ VALUE Al + A + (M + Al + (M + A + O/ B CON- AT N + O) Al)A) N + O) Al + N) (N + O) STANT 25° C. (%) (%) (%) (%) (%) (%) (K) (Ωcm) EXAMPLE 1 11 86 57 51 45 22 2211 2.E+04 EXAMPLE 2 6 92 90 50 47 132479 6.E+04 EXAMPLE 3 5 92 94 50 48 10 2588 7.E+04 EXAMPLE 4 12 82 61 4943 24 1802 4.E+02 EXAMPLE 5 12 82 56 49 42 25 1646 4.E+02

Next, since all the materials according to the Examples of the presentinvention were wurtzite-type phase films having strong orientation,whether the films have a strong a-axis orientation or c-axis orientationof the crystal axis in a vertical direction (film thickness direction)with respect to the Si substrate S was examined by XRD. At this time, inorder to examine the orientation of the crystal axis, the peak intensityratio of (100)/(002) was measured, where (100) is the hkl indexindicating a-axis orientation and (002) is the hkl index indicatingc-axis orientation.

Note that it was confirmed that a wurtzite-type single phase was formedin the same manner even when the thin film thermistor portion 3 wasdeposited on a polyimide film under the same deposition condition. Itwas also confirmed that the crystal orientation did not change even whenthe thin film thermistor portion 3 was deposited, on a polyimide filmunder the same deposition condition.

Exemplary XRD profiles of the materials according to the Examplesexhibiting strong c-axis orientation are shown in FIGS. 19 to 23. In theExample shown in FIG. 19, Al/(Ti+Sc+Al) was equal to 0.81(wurtzite-type, hexagonal), and measurement was performed at the angleof incidence of 1 degree. As can be seen from the result in thisExample, the intensity (100) was much stronger than that of (002).

In the Example shown in FIG. 20, Al/(Ti+Zr+Al) was equal to 0.84(wurtzite-type, hexagonal, and measurement was performed at the angle ofincidence of 1 degree.

In the Example shown in FIG. 21, Al/(Ti+Mo+Al) was equal to 0.93(wurtzite-type, hexagonal), and measurement was performed at the angleof incidence of 1 degree.

In the example shown, in FIG. 22, Al/(Ti+Nb+Al) was equal to 0.83(wurtzite-type, hexagonal), and measurement was performed at the angleof incidence of 1 degree.

In the Example shown in FIG. 23, Al/(Ti+W+Al) was equal to 0.76(wurtzite-type, hexagonal), and measurement, was performed at the angleof incidence of 1 degree.

As can be seen from she results in these Examples, the intensity of(002) was much stronger than that of (100).

The asterisk (*) in the graphs shows the peak originating from thedevice or the Si substrate with a thermal oxidation film, and thus, itwas confirmed that the peak with the asterisk (*) in the graphs wasneither the peak originating from, a sample itself nor the peakoriginating from an impurity phase. In addition, symmetrical measurementwas performed at a 0 degree angle of incidence, confirming that the peakindicated by (*) is lost in the symmetrical measurement, and thus, thatit was the peak originating from the device or the Si substrate with athermal oxidation film.

Next, the correlations between a crystal structure and its electriccharacteristic were compared with each. other in detail regarding theExamples of the present invention in which the wurtzite-type materialswere employed.

As shown in Tables 2 to 6, the crystal axis of some materials isstrongly oriented along a c-axis in a vertical direction with respect tothe surface of the substrate and that of other materials is stronglyoriented along an a-axis in a vertical direction with respect to thesurface of the substrate among the materials hawing neatly the sameAl/(T+A+Al) ratio, that is, Al/(Ti+Sc+Al) ratio, Al/(Ti+Zr+Al) ratio,Al/(Ti+Mo+Al) ratio, Al/(Ti+Nb+Al) ratio, or Al/(Ti+W+Al) ratio.

When both groups were compared to each other, it was found that thematerials having a strong c-axis orientation had a higher B constantthan that of the materials having a strong a-axis orientation providedthat they have nearly the same Al/(Ti+A+Al) ratio.

In addition, the crystal axis of some materials is strongly orientedalong a c-axis in a vertical direction with respect to the surface ofthe substrate and that of other materials is strongly oriented along ana-axis in a vertical direction with respect to the surface of thesubstrate among the materials having nearly the same Zr/(Ti+Sc),Zr/(Ti+Zr), Mo/(Ti+Mo), Nb/(Ti+Nb), or W/(Ti+W) ratio. Also in thiscase, it was found that the materials having a strong c-axis orientationhad a higher B constant than that of the materials having a stronga-axis orientation provided that they have nearly the same Zr/(Ti+Sc)ratio, Zr/(Ti+Zr) ratio, Mo/(Ti+Mo) ratio, Nb/(Ti+Nb) ratio, or W/(Ti+W)ratio.

When focus was placed on the amount of N (i.e., N/(Ti+A+Al+N+O), it wasfound that the materials having a strong c-axis orientation had aslightly larger amount of nitrogen than that of the materials having astrong a-axis orientation. Furthermore, when focus was placed on theamount of O (i.e., O/(N+O)), it was found that the materials hawing astrong a-axis orientation had a slightly larger amount of oxygen than,that of the materials having a strong c-axis orientation.

<Crystal Form Evaluation>

Next, as an exemplary crystal form in the cross-section of the than filmthermistor portion 3, a cross-sectional SEM photograph of the thin filmthermistor portion 3 according to the Example in the case where “M”=Ti,“A”=Sc (where Al/(Ti+Sc+Al)=0.81, wurtzite-type hexagonal, and strongc-axis orientation, in which the thin film thermistor portion 3 having athickness of about 430 nm was deposited on the Si substrate S with athermal oxidation film, is shown in FIG. 24.

A cross-sectional SEP photograph of the thin film thermistor portion 3according to the Example in the case where “M”=Ti, “A”=Zr (whereAl/(Ti+Zr+Al)=0.84, wurtzite-type hexagonal, and strong c-axisorientation) in which the thin film thermistor portion 3 having athickness of about 350 nm was deposited on the Si substrate S with athermal oxidation film, is also shown in FIG. 25.

A cross-sectional SEM photograph of the thin film thermistor portion 3according to the Example in the case where “M”=Ti, “A”=Mo (whereAl/(Ti+Mo+)=0.93, wurtzite-type hexagonal, and strong c-axisorientation), in which the thin film thermistor portion 3 having athickness of about 300 nm was deposited on the Si substrate S with athermal oxidation film, is also shown in FIG. 26.

A cross-sectional SEM photograph of the thin film thermistor portion 3according to the Example in the case where “M”=Ti, “A”=Nb (whereAl/(Ti+Nb+Al)=0.83, wurtzite-type hexagonal, and strong c-axisorientation, in which the thin, film thermistor portion 3 having athickness of about 300 nm was deposited on the Si substrate S with athermal oxidation film, is also shown in FIG. 27.

Furthermore, a cross-sectional SEM photograph of the thin filmthermistor portion 3 according to the Example in the case where “M”=Ti,“A”=W (where Al/(Ti+W+Al)=0.76, wurtzite-type hexagonal, and strongc-axis orientation), in which the thin film thermistor portion 3 havinga thickness of about 450 nm was deposited on the Si substrate S with athermal oxidation film, is also shown in FIG. 28.

The samples in these Examples were obtained by breaking the Sisubstrates 5 by cleavage. The photographs were taken by tilt observationat an angle of 45 degrees.

As can be seen from these photographs, the samples were formed of ahigh-density columnar crystal in all Examples. Specifically, the growthof columnar crystals in a vertical direction with respect to the surfaceof the substrate was observed both in the Examples revealing a strongc-axis orientation and in the Examples revealing a strong a-axisorientation. Note that, the break of the columnar crystal, was generatedupon breaking the Si substrate 5 by cleavage.

Regarding the site of a columnar crystal in the drawings, in the Examplerevealing a strong c-axis orientation shown in FIG. 24 in the case where“M”=Ti, “A”=Sc, the grain size was 10 nmφ (±5 nmφ and the length wasabout 350 nm. ran.

In the Example revealing a strong c-axis orientation shown in FIG. 25 inthe case where “M”=Ti, “A”=Zr, the grain size was 10 nmφ (±5 nmφ) andthe length was about 350 nm.

In the Example revealing a strong c-axis orientation shown in FIG. 26 inthe case where “M”=Ti, “A”=Mo, the grain size was 12 nmφ (±5 nmφ) andthe length was about 300 nm.

In the Example revealing a strong c-axis orientation shown in FIG. 27 inthe case where “M”=Ti, “A”=Nb, the grain size was 10 nmφ (±5 nmφ) andthe length was about 300 nm.

In the Example revealing a strong c-axis orientation shown in FIG. 28 inthe case where “M”=Ti, “A”=W, the grain size was 12 nmφ (±5 nmφ) and thelength was about 450 nm.

Note that the grain size here is the diameter of a columnar crystalalong the surface of a substrate and the length is that of a columnarcrystal in a vertical direction with respect to the surface of thesubstrate (film thickness).

When the suspect ratio of a columnar crystal is defined as “length/grainsize”, the materials according to the present Examples have an aspectratio of 10 or higher. It is contemplated that a film has a nigh-densitydue to the small grain size of a columnar crystal. It was also confirmedthat when a film having a thickness of 200 nm. 500 nm, or 1000 nm wasdeposited on a Si substrate S with a thermal oxidation film, a columnarcrystal having a high-density density was formed as described above.

<Heat Resistance Test Evaluation≦

In some of the materials according to the Examples and the ComparativeExamples shown in Tables 2 to 7, a resistance value and a B constantbefore and after the heat resist since test at a temperature of 125° C.for 1000 hours in air were evaluated. The results are shown in Tables 8to 12. The material according to Comparative Example made of aconventional Ta—Al—N-based material was also evaluated in the samemanner for comparison. In addition, a neat resistance test was performedon the thin film thermistor portion 3 made of the (M+A)-Al—N-basedmaterial (“M” represents at least one of Ti, V, Cr, Mn, Fe and Co, and“A” represents at least one of Sc, Zr, Mo, Nb, and W according toReference Example 1 (hexagonal wurtzite-type, strong c axis orientation)by reactive sputtering under a mixed gas (Ar gas+nitrogen gas;atmosphere containing no oxygen in the same manner for reference. Theresults are also shown in Tables 8 to 12.

As can be seen from these results, although the Al concentration and thenitrogen concentration vary, both the rising rate of a resistance valueand the rising rate of a B constant of the (M, A)_(x)Al_(y)(N,O)_(z)-based material (where “M” represents at least one of Ti, V, Cr,Mn, Fe, and Co, and “A” represents at least one of Sc, Zr, Mo, Nb, andW) are smaller than those of the Ta—Al—N-based material according to theComparative Example, and the heat resistance of the (M, A)_(z)Al_(y)(N,O)_(z)-based material (“M” represents at least one of Ti, V, Cr, Mn, Fe,and Co, and “A” represents at least one of Sc, Zr, Mo, Nb, and W) basedon the electric characteristic change before and after the heatresistance test is more excellent than that of the Ta—Al—N-basedmaterial according to the Comparative Example when the comparison ismade by using the materials according to the Examples basing a level ofB constant similar to that of the Comparative Example.

In addition, it is found that although the heat resistance of the(M+A.)-Al—based material according to Reference Example 1, which doesnot positively contain oxygen, is more excellent than that of theComparative Example, the (M+A)-Al—(N+O)-based material according toExample of the present invention, which positively contain oxygen, haslower rising rate of resistance valve and more excellent heat resistancecompared with Reference Example 1.

Note that, in the Ta—Al —N-based material, the ionic radius of Ta isvery large compared to that of Ti, Zr, Mo, Nb, and Al, and thus, awurtzite-type phase cannot be produced in the high-concentration Alregion. It is contemplated that the (M+A)-Al—N or (M+A)-Al—(N+O)-basedmaterial having a wurtzite-type phase has better heat resistance thanthe Ta—Al—N-based material because the Ta—Al—N-based material is not awurtzite-type phase.

TABLE 8 RISING RATE RISING RATE OF SPECIFIC OF B RESISTANCE CONSTANT AT25° C. AFTER AFTER HEAT SPECIFIC HEAT RESIS- RESISTANCE RESISTANCE TANCETEST TEST AT Al/ VALUE AT 125° C. 125° C. M + A M + A Al N O (M + Al)B25-50 AT 25° C. FOR 1,000 FOR 1,000 ELEMENT (%) (%) (%) (%) (%) (K) (Ωcm) HOURS (%) HOURS (%) COMPARATIVE TA 59 2 35 5 3 2688 6.E+02   12   6EXAMPLE EXAMPLE 2 Ti, Sc 9.1 38 47 6 81 2238 2.E+05  <1 <1 EXAMPLE 6 Ti,Sc 9.3 42 45 4 82 2015 1.E+05  <2 <1 REFERENCE Ti, Sc 9.5 43 47 — 822231 1.E+05  <4 <1 EXAMPLE 1

TABLE 9 RISING RATE RISING RATE OF SPECIFIC OF B RESISTANCE CONSTANT AT25° C. AFTER AFTER HEAT SPECIFIC HEAT RESIS- RESISTANCE RESISTANCE TANCETEST TEST AT Al/ VALUE AT 125° C. 125° C. M + A M + A Al N O (M + Al)B25-50 AT 25° C. FOR 1,000 FOR 1,000 ELEMENT (%) (%) (%) (%) (%) (K) (Ωcm) HOURS (%) HOURS (%) COMPARATIVE Ta 59 2 35 5 3 2888 6.E+02   12   6EXAMPLE EXAMPLE 4 Ti, Zr 8 41 46 5 84 2771 9.E+03  <2 <1 REFERENCE Ti,Zr 8 44 48 — 84 2764 7.E+03  <4 <1 EXAMPLE 1

TABLE 10 RISING RATE RISING RATE OF SPECIFIC OF B RESISTANCE CONSTANT AT25° C. AFTER AFTER HEAT SPECIFIC HEAT RESIS- RESISTANCE RESISTANCE TANCETEST TEST AT Al/ VALUE AT 125° C. 125° C. M + A M + A Al N O (M + Al)B25-50 AT 25° C. FOR 1,000 FOR 1,000 ELEMENT (%) (%) (%) (%) (%) (K) (Ωcm) HOURS (%) HOURS (%) COMPARATIVE Ta 59 2 35 5 3 2688 6.E+02   12   6EXAMPLE EXAMPLE 1 Ti, Mo 11 41 43 5 78 2576 2.E+03  <2 <1 REFERENCE Ti,Mo 12 42 46 — 78 2503 2.E+03  <4 <1 EXAMPLE 1

TABLE 11 RISING RATE RISING RATE OF SPECIFIC OF B RESISTANCE CONSTANT AT25° C. AFTER AFTER HEAT SPECIFIC HEAT RESIS- RESISTANCE RESISTANCE TANCETEST TEST AT Al/ VALUE AT 125° C. 125° C. M + A M + A Al N O (M + Al)B25-50 AT 25° C. FOR 1,000 FOR 1,000 ELEMENT (%) (%) (%) (%) (%) (K) (Ωcm) HOURS (%) HOURS (%) COMPARATIVE Ta 59 2 35 5 3 2688 6.E+02   12   6EXAMPLE EXAMPLE 1 Ti, Nb 8 42 48 2 83 2549 6.E+02  <2 <1 REFERENCE Ti,Nb 192 42 49 — 82 2447 6.E+02  <4 <1 EXAMPLE 1

TABLE 12 RISING RATE RISING RATE OF SPECIFIC OF B RESISTANCE CONSTANT AT25° C. AFTER AFTER HEAT SPECIFIC HEAT RESIS- RESISTANCE RESISTANCE TANCETEST TEST AT Al/ VALUE AT 125° C. 125° C. M + A M + A Al N O (M + Al)B25-50 AT 25° C. FOR 1,000 FOR 1,000 ELEMENT (%) (%) (%) (%) (%) (K) (Ωcm) HOURS (%) HOURS (%) COMPARATIVE Ta 59 2 35 5 3 2688 6.E+02   12   6EXAMPLE EXAMPLE 1 Ti, W 12 39 46 3 76 2454 2.E+03  <4 <2 REFERENCE Ti, W13 40 47 — 76 2350 1.E+03  <5 <2 EXAMPLE 1

The technical scope of the present invention is not limited to theaforementioned embodiments and Examples, but the present invention maybe modified in various ways without departing from the scope or teachingof the present invention.

Although in the above Examples, the metal nitride material for athermistor which consist of a metal nitride of (M, A) Al (N,O) (where“A” represents at least one of Sc, Zr, Mo, Nb, and W) was produced inthe case where “M” is Ti or Cr as an example, at least one of V, Mn, Fe,and Co can be substituted for at least part of Ti or Cr so as to obtainthe same characteristic.

REFERENCE NUMERALS

1: film type thermistor sensor, 2: insulating film, 3: thin filmthermistor portion, 4 and 124: pattern electrode

What is claimed is:
 1. A metal nitride material for a thermistor,consisting of a metal nitride represented by the general formula:(M_(1-v)A_(v))_(x)Al_(y)(N_(1-w)O_(w))_(z) (where “M” represents atleast one of Ti, V, Cr, Mn, Fe, and Co, “A” represents at least one ofSc, Zr, Mo, Nb, and W, 0.0<v<1.0, 0.70≦y/(x+y) ≦0.98, 0.45≦z≦0.55,0w≦0.35, and x+y+z=1), wherein the crystal structure thereof is ahexagonal wurtzite-type single phase.
 2. The metal nitride material fora thermistor according to claim 1, wherein the metal nitride material,is deposited as a film and is a columnar crystal, extending in avertical direction with respect to the surface of the film.
 3. The metalnitride material for a thermistor according to claim 2, wherein themetal nitride material is deposited as a film and is more stronglyoriented along a c-axis than an a-axis in a vertical direction withrespect to the surface of the film.
 4. A film type thermistor sensorcomprising: an insulating film; a thin film thermistor portion made ofthe metal nitride material for a thermistor according to claim 2 on theinsulating film; and a pair of pattern electrodes formed at least on thetop or the bottom of the thin film thermistor portion.
 5. A method forproducing the metal nitride material for a thermistor according to claim2, the method comprising: a deposition step of performing filmdeposition by reactive sputtering in a nitrogen- and oxygen-containingatmosphere using an M-A-Al (where “M” represents at least one of Ti, V,Cr, Mn, Fe, and Co, and “A” represents at least one of Sc, Zr, Mo, Nb,and W) alloy sputtering target.
 6. The metal nitride material, for athermistor according to claim 1, wherein the metal nitride material isdeposited as a film and is more strongly oriented along a c-axis than,an a-axis in a vertical direction with respect to the surface of thefilm.
 7. A film type thermistor sensor comprising: an insulating film; athin film thermistor portion made of the metal nitride material for athermistor according to claim 6 on the insulating film; and a pair ofpattern electrodes formed at least on the top or the bottom of the thinfilm thermistor portion.
 8. A film type thermistor sensor comprising: aninsulating film; a thin film thermistor portion made of the metalnitride material for a thermistor according to claim 1 on the insulatingfilm; and a pair of pattern electrodes formed at least on the top or thebottom of the thin firm thermistor portion.
 9. A method for producingthe metal nitride material for a thermistor according to claim 6, themethod comprising: a deposition step of performing film deposition byreactive sputtering in a nitrogen- and oxygen-containing atmosphereusing an M-A-Al (where “M” represents at least one of Ti, V, Cr, Mn, Fe,and Co, and “A” represents at least one of Sc, Zr, Mo, Nb, and alloysputtering target.
 10. A method for producing the metal nitride materialfor a thermistor according to claim 1, the method comprising: adeposition step of performing film deposition by reactive sputtering ina nitrogen- and oxygen-containing atmosphere using an M-A-Al (where “M”represents at least one of Ti, V, Cr, Mn, Fe, and Co, and “A” representsat least one of Sc, Zr, Mo, Nb, and W) alloy sputtering target.